Advanced Characterization of Nanoporous Gold

A.A. El-Zoka, R.C. Newman, B. Langelier
University of Toronto,
Canada

Keywords: nanoporous gold, atom probe tomography, 3D characterization, dealloying, nanomaterials

Summary:

The interest in nanoporous metals, formed by controlled dealloying of noble metal alloys, has been increasing due to the promising capabilities of such materials. The functionality of NPG is heavily affected by attributes such as ligament size, and local and global chemical composition [1,2]. Realizing the full potential behind NPG as a functional material can only be facilitated by the analysis of the porous structure at its natural length scale – that is, the nanometre scale [3]. Atom Probe Tomography (APT) is capable of providing 3D analysis of many materials at the nanometer, and even sub-nanometer scale. Due to the high porosity, APT on NPG was deemed as difficult. Pores are highly likely to result in mechanical failure of the sample during analysis [4,5]. To provide structural support to the porous layer, elimination of porosity was achieved through inner-pore electrodeposition of Cu. As a result, atomic scale chemical mapping of the porous structure was achieved (figures 1-3). Due to the efficiency of the Cu filling, a larger volume of NPG-Cu was analyzed by APT, compared to that presented in Pfeiffer’s work, was obtained [5]. Ag77-Au22-Pt1 alloy. Such porous materials have finer ligament and pore sizes [6]. In an effort to understand the refining effect of Pt and the mechanism involved, APT was performed. In addition to chemical profiling of individual ligaments, chemical profiling across the dealloying interface and the extent of Pt redistribution in the dealloyed layer were analyzed. To extend and clarify the main observations inferred from the APT of NPG-1Pt, APT data on NPG-3Pt are currently being analyzed, to be correlated with STEM tomography.